Kirk McKusick 4ed62fbd7f The only known cause of this panic is running out of disk space. ... The problem occurs when an indirect block and a data block are being allocated at the same time. For example when the 13th block of the file is written, the filesystem needs to allocate the first indirect block and a data block. If the indirect block allocation succeeds, but the data block allocation fails, the error code dellocates the indirect block as it has nothing at which to point. Unfortunately, it does not deallocate the indirect block's associated dependencies which then fail when they find the block unexpectedly gone (ptr == 0 instead of its expected value). The fix is to fsync the file before doing the block rollback, as the fsync will flush out all of the dependencies. Once the rollback is done the file must be fsync'ed again so that the soft updates code does not find unexpected changes. This approach is much slower than writing the code to back out the extraneous dependencies, but running out of disk space is not expected to be a common occurence, so just getting it right is the main criterion. PR: kern/15063 Submitted by: Assar Westerlund <assar@stacken.kth.se>		2000-01-11 08:27:00 +00:00
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ffs	The only known cause of this panic is running out of disk space.	2000-01-11 08:27:00 +00:00
mfs	Second pass commit to introduce new ACL and Extended Attribute system	1999-12-19 06:08:07 +00:00
ufs	Several performance improvements for soft updates have been added:	2000-01-10 00:24:24 +00:00